Background:

Niraparib hydrochloride (MK-4827 hydrochloride) is a highly potent and orally bioavailable PARP1 and PARP2 inhibitor with IC50s of 3.8 and 2.1 nM, respectively. Niraparib hydrochloride (MK-4827 hydrochloride) leads to inhibition of repair of DNA damage and shows anti-tumor activity[1][2][3].

Niraparib inhibits PARP activity with EC50=4 nM and EC90=45 nM in a whole cell assay. Niraparib inhibits proliferation of cancer cells with mutant BRCA-1 and BRCA-2 with CC50 in the 10?100 nM range. Niraparib displays excellent PARP 1 and 2 inhibition with IC50=3.8 and 2.1 nM, respectively, and in a whole cell assay[1]. To validate that Niraparib inhibits PARP in these cell lines, A549 and H1299 cells are treated with 1 μM Niraparib for various times and measured PARP enzymatic activity using a chemiluminescent assay. The results show that Niraparib inhibits PARP within 15 minutes of treatment reaching about 85% inhibition in the A549 cells at 1 h and about 55% inhibition at 1 h for the H1299 cells[2].

Niraparib is well tolerated and demonstrates efficacy as a single agent in a xenograft model of BRCA-1 deficient cancer. Niraparib is well tolerated in vivo and demonstrates efficacy as a single agent in a xenograft model of BRCA-1 deficient cancer. Niraparib is characterized by acceptable pharmacokinetics in rats with plasma clearance of 28 (mL/min)/kg, very high volume of distribution (Vdss=6.9 L/kg), long terminal half-life (t1/2=3.4 h), and excellent bioavailability, F = 65%[1]. Niraparib enhances radiation response of p53 mutant Calu-6 tumor in both cases, with the single daily dose of 50 mg/kg being more effective than 25 mg/kg given twice daily[3].

参考文献:
[1]. Jones P, et al. Discovery of 2-{4-[(3S)-piperidin-3-yl]phenyl}-2H-indazole-7-carboxamide (MK-4827): a novel oral poly(ADP-ribose)polymerase (PARP) inhibitor efficacious in BRCA-1 and -2 mutant tumors. J Med Chem. 2009 Nov 26;52(22):7170-85.
[2]. Bridges KA, et al. Niraparib (MK-4827), a novel poly(ADP-Ribose) polymerase inhibitor, radiosensitizes human lung and breast cancer cells. Oncotarget. 2014 Jul 15;5(13):5076-86.
[3]. Wang L, et al. MK-4827, a PARP-1/-2 inhibitor, strongly enhances response of human lung and breast cancer xenografts to radiation. Invest New Drugs. 2012 Dec;30(6):2113-20.
[4]. Mirza MR, et al. Niraparib Maintenance Therapy in Platinum-Sensitive, Recurrent Ovarian Cancer. N Engl J Med. 2016 Dec 1;375(22):2154-2164.